The present invention relates to a disk drive for use in recording and reproducing data on a disk-shaped recording medium such as a magnetic disk and, in particular, to a carriage mechanism of the disk drive.
Referring to FIGS. 1 through 3, a conventional magnetic disk drive designed for magnetic disks will be described. Such a magnetic disk drive is disclosed in, for example, Japanese Patent Laid-Open (JP-A) No. 9-91943. In the magnetic disk drive illustrated in FIG. 1, a reception mechanism and an ejection mechanism for receiving and ejecting a magnetic disk, respectively, are omitted for clarity of illustration. A chassis 10 comprises a pair of side walls 10-1 on both sides thereof. All components and parts are mounted on a principal surface of the chassis 10. A main printed wiring board 11 and a subsidiary printed wiring board 20 are fixed by screws to the principal surface of the chassis 10. For the main printed wiring board 11, two support members 10-2 (FIG. 2) are formed integrally with the chassis 10 by cutting and rising corresponding portions of a principal plate of the chassis 10. The main printed wiring board 10 is fixed onto the support members 10-2 by the use of screws 12.
A stepping motor 13 is attached to a rear wall 10-3 at a rear end of the chassis 10. An output shaft 13-1 of the stepping motor 13 penetrates through the rear wall 10-3. The output shaft 13-1 has a top end rotatably supported by a shaft receptacle 10-4 integrally formed with the chassis 10 by cutting and rising a corresponding portion of the principal plate of the chassis 10. The output shaft 13-1 has a threaded outer peripheral surface. A carriage mechanism 14 is provided with an arm 14-1 with a pin 14-2 embedded therein. The pin 14-2 is engaged with the threaded outer surface of the output shaft 13-1. With this structure, rotation of the output shaft 13-1 brings about the movement of the carriage mechanism 14 in the same direction as the output shaft 13-1. On the carriage mechanism 14, magnetic heads are mounted for access to the magnetic disk. The carriage mechanism 14 serves to move the magnetic heads in the radial direction of the magnetic disk.
The carriage mechanism 14 is provided with a U-shaped bearing arm 14-3 formed on the side opposite to the arm 14-1. A guide bar 15 penetrates through the bearing arm 14-3. The guide bar 15 is held by a guide bar clamp 16. With this structure, the carriage mechanism 14 is guided by the guide bar 15 during the movement following the rotation of the output shaft 13-1. The guide bar clamp 16 is fixed by a screw to a support plate 10-5 (FIG. 2). The support plate 10-5 is formed integrally with the chassis 10 by cutting and rising a corresponding portion of the principal plate of the chassis 10, and projects upward through a hole formed in the main printed wiring board 11.
In FIG. 3, a motor 21 for rotating the magnetic disk and other circuit components (not shown) are mounted on a subsidiary printed wiring board 20 only on the upper surface thereof. Accordingly, the subsidiary printed wiring board 20 is fixed to the principal plate of the chassis 10 by the screws 12 (FIG. 1) to be substantially in contact therewith at the position closer to a slot for the magnetic disk, i.e., to a front bezel 17.
The structure of the motor 21 will briefly be described. The motor 21 comprises a rotation shaft 21-1, a center metal 21-2, a plurality of cores 21-3, a plurality of stator coils 21-4, a ring-shaped permanent magnet 21-5, and a circular casing 21-6 attached to the rotation shaft 21-1. The center metal 21-2 has a cylindrical shape and serves as a bearing. Each of the cores 21-3 radially outwardly extends from the center. Each of the stator coils 21-4 is wound around an end portion of each corresponding core 21-3. The permanent magnet 21-5 surrounds these cores 21-3. The casing 21-6 holds the permanent magnet 21-5. When the rotation shaft 21-1 is rotated, the permanent magnet 21-5 and the casing 21-6 rotate together with the rotation shaft 21-1. A reference numeral 21-7 depicts an index magnet. A combination of the cores 21-3 and the stator coils 21-4 serves as a stator of the motor 21. A combination of the permanent magnet 21-5 and the casing 21-6 serves as a rotor of the motor 21. The stator and the rotor of the type are disclosed in, for example, Japanese Patent Laid-Open (JP-A) No. 9-91866 and, therefore, will not be described in detail.
The casing 21-6 has a protruding portion formed at its center and a flat portion 21-6a formed on an upper surface of the protruding portion. To the flat portion 21-6a, a disk table 21-8 formed by a plastic magnet is integrally fixed. The flat portion 21-6a is provided with an arm 22 attached to a bottom surface thereof. A drive roller 23 is rotatably mounted on the arm 22. Each of the flat portion 21-6a and the disk table 21-8 has a generally rectangular hole formed therein. Through these holes, the drive roller 23 projects upward from the disk table 21-8. The magnetic disk received in the magnetic disk drive is placed on the disk table 21-8. The drive roller 23 is inserted in and engaged with a hole formed in a hub of the magnetic disk. Thus, the magnetic disk is rotated following the rotation of the rotor. The disk table 21-8 is disclosed in, for example, Japanese Patent Laid-Open (JP-A) No. 9-91814 and is not described in detail herein.
Above the motor 21, an eject plate 24 and a disk holder unit 25 are incorporated as the ejection mechanism the reception mechanism for the magnetic disk, respectively. The eject plate 24 and the disk holder unit 25 are also disclosed in the above-mentioned Japanese Patent Laid-Open (JP-A) No. 9-91814 or 9-91943. The chassis 10 is coupled with a cover plate 18 to protect an internal space inside the chassis 10.
In the above-mentioned disk drive, the motor 21 is mounted on the principal surface of the chassis 10, in other words, built inside the chassis 10. With this structure, magnetic flux generated from the stator coil 21-4 or the permanent magnet 21-5 acts on the magnetic head to adversely affect data reading or writing operation. Moreover, since the motor 21 is built inside the chassis 10, a greater part of a limited space on the principal surface of the chassis 10 is occupied by the motor 21. This inevitably restricts a mounting space for other mechanisms. In order to solve the above-mentioned problems, the present inventors have proposed, as a previous technique, a disk drive illustrated in FIG. 4 (Japanese Patent Application No. 10-1988 published as a JP-A 11-203767 on Jul. 30, 1999). FIG. 4 shows a characteristic part of the magnetic disk drive, including a chassis 30 and a drive motor 40 (hereinafter simply referred to as a motor) attached to the chassis 30 for rotating a magnetic disk.
The chassis 30 bears a reception mechanism for receiving a magnetic disk, an ejection mechanism for ejecting the magnetic disk that has been received, a carriage mechanism which has a head unit for accessing the magnetic disk and which carries the head unit so that the head unit is movable in a radial direction of the magnetic disk, and a moving mechanism for moving the carriage mechanism. All of these components are mounted on a principal surface of the chassis 30, i.e., an upper surface in FIG. 4. These components are well known in the art and will not be described herein. In other words, a feature of this embodiment lies in installation of the motor 40 in the chassis 30. Other configurations are basically similar to those of the conventional disk drive.
The motor 40 is similar in structure to the motor 21 described in conjunction with FIG. 3 and comprises a rotor 41 and a stator 42 combined with the rotor 41. The rotor 41 has a disk-shaped metallic casing 41-1. The casing 41-1 has a protruding portion 41-11 formed at its center to protrude upward. The protruding portion 41-11 has an upper surface to which a disk table 43 is mounted. The chassis 30 has an opening 30a which allows only an upper part of the protruding portion 41-11 to pass therethrough and project on the principal surface. Thus, the disk table 43 is projected on the principal surface of the chassis 30.
A rotation shaft 44 of metal is integrally fixed to the rotor 41 at the center thereof to pass through the casing 41-1 and the disk table 43. When the disk table 43 is injection-molded by the use of a plastic magnet, the casing 41-1 and the rotation shaft 44 are integrally assembled. The casing 41-1 has a cylindrical member 41-12 formed on its outer periphery to extend downward. A ring-shaped permanent magnet 45 is attached to an inner surface of the cylindrical member 41-12.
As described in conjunction with FIG. 3, the protruding portion 41-11 is provided with an arm 46 attached to a bottom surface thereof. A drive roller 47 is rotatably mounted on the arm 46. Each of the protruding portion 41-11 and the disk table 43 has a generally rectangular hole formed therein. Through these holes, the drive roller 47 projects upward from the disk table 43. The magnetic disk received in the magnetic disk drive is placed on the disk table 43. The drive roller 47 is inserted in and engaged with a hole formed in a hub of the magnetic disk. Thus, the magnetic disk is rotated following the rotation of the rotor 41.
On the other hand, the stator 42 is attached to a back surface of the chassis 30 by means of a metallic motor chassis 50 of metal. More specifically, the stator 42 is formed on a printed wiring board 51 mounted on the principal surface of the motor chassis 50. As described in conjunction with FIGS. 3 and 4, the stator 42 comprises a plurality of stator cores 42-1, a plurality of stator coils 42-2, and a bearing unit (center metal) 42-3. Each of the stator cores 42-1 extends radially outwardly from an outer periphery of a ring-shaped member of metal. Each of the stator coils 42-2 is wound around an end portion of each corresponding core 42-1. The bearing unit 42-3 is formed at the center of the printed wiring board 51 and supports the rotation shaft 44. The motor chassis 50 has a plurality of attaching elements 50-1 of an inverted-L shape which extend upward from a peripheral edge of the motor chassis 50 to abut against the back surface of the chassis 30.
A main printed wiring board corresponding to the main printed wiring board 11 described in conjunction with FIG. 3 is also mounted on the back surface of the chassis 30. With this structure, the receiving and the ejecting mechanisms for the magnetic disk, the carriage mechanism movably holding the magnetic disk, and the moving mechanism for moving the carriage mechanism can easily be mounted in the space on the principal surface of the chassis 30.
In the disk drive illustrated in FIG. 4, it is essential to provide a component for suppressing vibration or shock given to the chassis 30. Such a component can easily be implemented by a lower cover attached to the back surface of the chassis 30. However, the lower cover must be attached to the chassis 30 with flexibility in addition to sufficient mechanical strength against the vibration or the shock. The reason is given below. The disk drive of the type is generally combined with an electronic apparatus such as a personal computer and used as a memory device. The combination is achieved by fixing the lower cover with screws to an attaching element of the electronic apparatus. Typically, such fixation by the screws is carried out at a plurality of positions so that the lower cover is susceptible to mechanical strain. If the mechanical strain is transmitted from the lower cover to the chassis 30, the chassis 30 may be deformed to result in malfunction or operation error of a movable member formed on the principal surface of the chassis 30. In view of the above, it is necessary to attach the lower cover to the chassis 30 with flexibility.